Image processing apparatus and method and storage medium

ABSTRACT

It is an object to provide an adding technique for enabling additional information to be certainly decoded from an image to which two or more kinds of additional information was added to an input image so that it is difficult to discriminate by the human eyes. To accomplish this object, for example, a plurality of kinds of additional information is periodically added to the input image at different periods so that it is difficult to discriminate by the human eyes. The image to which those additional information was added is outputted to an image forming unit.

This application is a division of application Ser. No. 09/113,358, filedJul. 10, 1998 now U.S. Pat. No. 6,320,675 issued Nov. 20, 2001.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to image processing apparatus and method having afunction to add additional information to an input image and relates toa storage medium in which such a method has been stored.

2. Related Background Art

In recent years, the performance of an image processing apparatus suchas color printer, color copying apparatus, or the like has been improvedand an image of a high picture quality can be provided. Thus, an imagecan be being formed with a picture quality almost similar to that of abill, securities, or the like.

However, the formation of such an image is inhibited and it is necessaryto suppress such illegal behavior. As one of countermeasures for thispurpose, there has been known a technique to bury a dot pattern showingthe numbers (information such as manufacturing number, product number,user ID, and the like) which are peculiar to the image processingapparatus into each image to be formed. By performing such a process,even if an image is illegally formed, by analyzing the dot patternburied in the formed image, various situations at a time when the imageis formed can be also known.

The dot pattern is periodically buried into the whole image everypredetermined periods. Therefore, even if only a part of the imageexists, since the information has been buried in this partial portion,the search of the various information as mentioned above can beexecuted.

To perfectly search the various information, an area of the partialportion in the image needs to be set to an area corresponding to atleast one period among the above periods.

A conventional adding method of the dot pattern (additional information)as mentioned above differs every manufacturer who manufactures each ofthe image processing apparatus. To decode the additional informationsuch as a manufacturing number and the like on the basis of a certainformed image, it is necessary to sequentially use a decoding methodcorresponding to the adding method of each manufacturer.

However, hitherto, there is a problem such that the additionalinformation (manufacturing number, product number, user ID, and thelike) added to the image which is finally formed cannot be decoded atall due to a cause such that the image process of the input image hassome periodic trouble, the original image contents are periodic, or thelike.

Particularly, the problem as mentioned above is likely to occur in thecase where an area of the formed image is small like a stamp or the likerather than the case where an area of the formed image is large like abill or the like.

Hitherto, in the case where the number of manufacturers who manufacturethe apparatuses is large, there is a problem such that a load tosequentially use the decoding methods as mentioned above is large. Inparticular, such a problem typically appears in case of performing theabove decoding by a software process or the like.

SUMMARY OF THE INVENTION

The invention is made in consideration of the foregoing conventionaltechnique and it is an object to provide an adding technique forenabling additional information to be certainly decoded from an imageobtained by adding two or more kinds of additional information has beenadded to an input image so that it is difficult to discriminate by thehuman eyes.

For example, it is an object of the invention to enable informationhaving a high significance to be decoded as much as possible in case ofburying two or more kinds of additional information into an input image.

To accomplish the above objects, according to one preferred embodimentof the invention, there is provided an image processing apparatuscomprising:

adding means for periodically adding first additional information to aninput image by a first period so that it is difficult to discriminate bythe human eyes and for periodically adding second additional informationdifferent from the first additional information by a second perioddifferent from the first period so that it is difficult to discriminateby the human eyes; and

output means for outputting the image to which predetermined additionalinformation was added by the adding means to an image forming unit.

According to another embodiment, there is provided an image processingapparatus comprising:

adding means for adding information consisting of first additionalinformation and second additional information to an input image everyunit area which is periodically assigned;

switching means for switching a positional relation between an areashowing the first additional information and an area showing the secondadditional information in the unit area; and

output means for outputting the image to which predetermined additionalinformation was added by the adding means to an image forming unit.

According to still another embodiment, there is provided an imageprocessing apparatus comprising:

adding means for adding first additional information to an input imageby a first method so that it is difficult to discriminate by the humaneyes and for adding second additional information by a second method sothat it is difficult to discriminate by the human eyes; and

output means for outputting the image to which predetermined additionalinformation was added by the adding means to an image forming unit,

wherein the first additional information is information which canspecify the second method.

According to further another embodiment, there is provided an imageprocessing apparatus comprising:

adding means for adding first additional information including an errorcorrection code having a first error correcting ability to an inputimage so that it is difficult to discriminate by the human eyes and foradding second additional information including an error correction codehaving a second error correcting ability different from the first errorcorrecting ability so that it is difficult to discriminate by the humaneyes; and

output means for outputting the image to which predetermined additionalinformation was added by the adding means to an image forming unit.

The above and other objects and features of the present invention willbecome apparent from the following detailed description and the appendedclaims with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a detailed diagram of an additional dot generation unit 212;

FIG. 2 is a diagram showing a state where AddOn dots were added;

FIG. 3 is a diagram showing an example of an image processing apparatus;

FIG. 4 is a diagram showing a procedure for image processes;

FIG. 5 is a detailed diagram of the basic additional dot generation unit212;

FIG. 6 is a diagram showing a state in a register;

FIG. 7 is a diagram showing an example of AddOn dots;

FIG. 8 is a diagram showing a state where the AddOn dots were added;

FIG. 9 is a diagram for explaining an adding method of an AddOn pattern;

FIG. 10 is a diagram showing a state where the AddOn dots were added;

FIG. 11 is a diagram showing an example of an image processingapparatus;

FIG. 12 is a diagram showing a state where additional information wasadded to an input image;

FIG. 13 is a diagram showing a state of a register to store a trackingcode (additional information);

FIG. 14 is a block diagram of an AddOn dot adding processing unit;

FIG. 15 is a diagram for explaining an expressing method of informationby AddOn dots;

FIG. 16 is a diagram showing a code shown by each AddOn line;

FIG. 17 is a diagram showing parity bits of a manufacturer ID;

FIG. 18 is a diagram showing a procedure for decoding additionalinformation from an image to which the additional information was added;and

FIG. 19 is a conceptual diagram of additional information of amanufacturer ID, a product name, and a manufacturing number.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The first embodiment of the present invention will now be describedhereinbelow.

FIG. 3 is a diagram showing an image processing apparatus using a colorelectrophotographing technique which is used in the embodiment. In thediagram, reference numeral 214 denotes a printer controller(hereinafter, referred to as a controller), which will be explainedhereinlater. The controller receives image data of R, G, and B eachconsisting of eight bits per color inputted from a host computer servingas external equipment, executes well-known color image processes, andafter that, outputs the processed image data to a printer engine at thepost stage as image data of M (magenta), C (cyan), Y (yellow), and K(black) each consisting of 8 bits per color.

Reference numeral 215 denotes a printer engine (hereinafter, referred toas an engine), which will be explained hereinlater. The engine outputsthe inputted color image data of MCYK as a laser beam L modulated on thebasis of an image of each color.

A charging device 101 uniformly charges a photosensitive drum 100 to apredetermined polarity. For example, a first latent image is formed inmagenta onto the photosensitive drum 100 by an exposure of the laserbeam L.

In this case, a predetermined development bias voltage is subsequentlyapplied to only a developing device Dm of magenta. A latent image ofmagenta is developed. A first toner image of magenta is formed on thephotosensitive drum 100.

A transfer paper P is fed at a predetermined timing. Just before thefront edge of the paper reaches a transfer start position, a transferbias voltage (+1.8 kV) of a polarity (for example, plus polarity)opposite to the polarity of toner is applied to a transfer drum 102. Thepaper is electrostatically adsorbed onto the surface of thephotosensitive drum 100. After that, the first toner image on thephotosensitive drum 100 is transferred onto the transfer paper P and, atthe same time, the transfer paper P is electrostatically adsorbed ontothe surface of the transfer drum 102. Subsequently, the magenta tonerremaining on the photosensitive drum 100 is removed by a cleaner 103,thereby preparing for the latent image formation and a developing stepof the next color.

A second latent image of cyan is subsequently formed on thephotosensitive drum 100 by the laser beam L. The second latent image onthe photosensitive drum 100 is formed by a developing device Dc of cyan,so that a second toner image is formed. The second toner image of cyanis transferred onto the transfer paper P so as to be matched to theposition of the first latent image of magenta which has already beentransferred onto the transfer paper P. In the transfer of the tonerimage of the second color, a bias voltage of +2.1 kV is applied to thetransfer drum 102 just before the transfer paper P reaches the transferunit.

Similarly, third and fourth latent images of yellow and black aresequentially formed on the photosensitive drum 100 and are sequentiallydeveloped by developing devices Dy and Db, respectively. Third andfourth toner images of yellow and black are sequentially transferred soas to be matched to the position of the toner image which has alreadybeen transferred to the transfer paper P. Thus, the toner images of fourcolors are formed on the transfer paper P in an overlapped state.

FIG. 4 is a block diagram showing an image processing procedure. Colorimage data of RGB is transmitted in parallel from a host computer 201serving as external equipment and is inputted to the controller 214.

A color conversion processing unit 202, a γ (gamma) correction unit 203,and a half tone processing unit 204 are arranged in the controller 214.Processes such as masking and UCR are executed to the inputted RGBsignals by the color conversion processing unit 202 and a colorcorrection and an undercolor removal are executed, so that they areconverted into image data of magenta (M), cyan (C), yellow (Y), andblack (K). Since the image processing apparatus prints every pictureplane of each color of Y, M, C, and K, the image data is areasequentially outputted from the color conversion processing unit 202,namely, in accordance with the order of the data of one picture plane ofM, the data of one picture plane of C, the data of one picture plane ofY, and the data of one picture plane of K.

Subsequently, the image data is corrected by the γ correction unit sothat an output density curve becomes linear. A half tone process isexecuted by the half tone processing unit 204 by a method such assystematic dither method, error diffusing method, or the like.

After the above processes were executed in the controller 214, the imagedata of M, C, Y, and K is area sequentially inputted to the engine 215.

The engine 215 is constructed by an AddOn adding processing unit 205, aPWM (Pulse Width Modulation) processing unit 206, a laser drive unit207, an additional dot generation unit 212, an EEPROM 213, and the like.

The AddOn adding processing unit 205 buries enciphered information (dotpattern) as necessary into the image data of M, C, Y, and K inputtedfrom the controller 214 in accordance with the signal which is inputtedfrom the additional dot generation unit 212 and outputs the resultantimage data to the PWM processing unit 206. In the embodiment, an AddOnpattern is added to only the image data of yellow (Y) which is inputtedand the resultant image data is outputted. This is because a featuresuch that the image of yellow (Y) is difficult to be discriminated bythe human eyes rather than the images of the other colors (M, C, K) isused.

After that, the image data is pulse width modulated by the PWMprocessing unit 206 and is D/A converted. After that, the convertedanalog signal is inputted to the laser drive unit 207 and is printed.

A CPU 302 is provided in the engine 215 and executes a control of eachblock in the engine and transmission and reception of data to/from therespective blocks.

FIG. 5 is a block diagram of the basic additional dot generation unit212 to bury additional information into an image. Fake tracking codes(additional information) stored in the EEPROM 213 are loaded into aregister 301 in the CPU 302 when the image processing apparatus isactivated.

FIG. 6 shows an internal construction of the register 301. Codes arestored in addresses F000 to F005 in the register. Total twelve bitsconsisting of eight bits of the address F000 and upper four bits of theaddress F001 shown in hatched portions in the diagram correspond to anarea to store a code of a manufacturer ID (ID of the manufacturer whomanufactured the image processing apparatus, printer controller 214, orprinter engine 215). Among them, 8 bits indicate the code of the actualmanufacturer ID and remaining 4 bits are parity bits for parity check.

Codes of the factory ID of the manufacturer who manufactured the imageprocessing apparatus, the apparatus number, the model number, and thelike are stored in the other areas (lower four bits of the address F001and the addresses of F002 to F005). The parity bits for parity check arealso similarly added and stored in those registers.

When the image processing apparatus starts the printing operation, thosevalues are enciphered by an encipherment circuit 305 and a parity ischecked by a parity check 306. If there is an error here, the printingoperation is stopped.

A main scan counter 307 transmits an ON signal at a position where AddOndots should be added in accordance with a clock signal PCLK in the mainscan direction of the image data. A subscan counter 308 performs acounting operation in response to a clock signal BD in the subscandirection and transmits an ON signal in an AddOn line. An AddOn dotgeneration circuit 309 receives an AddOn dot shape parameter which isstored in an ROM 303 of the CPU. The circuit 309 generates AddOn dotsonly when all of an AddOn permission signal which is turned on only whenthe yellow data is transmitted, the main scan counter 307, and thesubscan counter 308 are ON. In an FF (the highest density) area, K isset to ON and in a 00 (the lowest density) area, WH (white) is set toON, and they are transmitted. In the AddOn adding processing unit 205 inFIG. 4, when K is inputted, the image data at the position of thecorresponding image is forcedly modulated to the highest density. WhenWH is inputted, it is modulated to the lowest density.

FIG. 7 is an example (enlarged diagram) of the AddOn dots. A broken linein the diagram shows an AddOn line (in the embodiment, it is assumedthat one AddOn line has a thickness of four pixels) of the n-th line inthe image. Reference numeral 404 denotes an AddOn dot and 405 indicatesan enlarged dot of the AddOn dot. The AddOn dot is formed by an FF area401 and 00 areas 402 and 403 located on both sides of the FF area 401.As mentioned above, the AddOn dot 404 is added to the AddOn line for amulti-value image (plane of yellow). As will be explained hereinlater, aphase difference between the AddOn dots can be used as variousadditional information.

FIG. 8 shows a state of a formed image in the yellow plane derived bythe addition of the basic additional information (AddOn dot) executed bythe additional dot generation unit 212 in FIG. 5. Reference numeral 1201corresponds to the AddOn dots 404 and 405.

An area 1202 shown by a×b denotes a size of image area which can expressall of the additional information, namely, an image size of one periodto add the additional information. All of the codes stored in theregister in FIG. 6 can be expressed by the dots added in the area 1202.

A plurality of AddOn dots 1201 in the area 1202 are repetitively addedto the whole image. In the present description, 16 lines 1203 calledAddOn lines exist in the area of one period in the main scan direction.The AddOn dots 1201 are arranged one by one on each AddOn line.

By adding reference dots 1204 onto the zeroth and seventh AddOn lines,the start (head AddOn line) of one period and the direction of the AddOnline can be specified. The manufacturer ID and the other additionalinformation (factory ID, apparatus number, model number, and the like)added by the additional dot generation unit 212 in FIG. 5 are alwaysadded at predetermined positions in the area 1202, respectively.Specifically speaking, four AddOn lines from the head correspond to theportion which always shows the manufacturer ID and the remaining AddOnlines correspond to the portion showing the other additionalinformation.

How to show various codes (additional information) by a plurality ofAddOn dots will now be described with reference to the drawings. FIG. 9enlargedly shows the n-th and (n+1)th AddOn lines.

T denotes the repeating period of the AddOn pattern in the main scandirection. That is, AddOn dots 901 and 903 have similar roles andinformation is not shown by AddOn dots 901 and 902.

In the embodiment, it is assumed that information is expressed by aphase difference between the AddOn lines before and after the presentline in the area 1202. By assigning phase differences like 0 to 7 in thediagram, information of three bits can be shown by each AddOn line.Since there are 16 AddOn lines in FIG. 8, information of 48 bits can beexpressed and all of the codes stored in the register 301 can be added.

In FIG. 9, t denotes a phase difference between the AddOn dots 901 and903 and shows 3-bit information of “2”, namely, “010” in this case.

The basic construction when adding additional information to the inputimage has been described above. A characteristic construction of theembodiment will now be described hereinbelow.

In the embodiment, a construction of the foregoing additional dotgeneration unit 212, namely, a method of adding the manufacturer ID andthe other information differs. The adding method will now be describedin detail hereinbelow. Since the basic construction of the imageprocessing apparatus shown in FIGS. 3 and 4 is similar to that mentionedabove, its description is omitted.

FIG. 1 is a detailed diagram showing the additional dot generation unit212, EEPROM 213, and CPU 302 in the embodiment. Component elementssimilar to those in FIG. 5 are designated by the same reference numeralsand their descriptions are omitted.

The fake tracking codes (additional information) stored in the EEPROM213 are loaded into the register 301 in the CPU 302 when the imageprocessing apparatus is activated. Data which is loaded into theregister 301 is data similar to that in FIG. 6.

Reference numerals 501 and 502 denote switching units for simultaneouslyperforming the switching operations, which will be explainedhereinlater, by the CPU 302 every predetermined AddOn line when theAddOn dots showing the manufacturer ID are formed and when the AddOndots showing the other additional information are formed.

The CPU 302 has the switching unit 501 for counting the AddOn lines bycounting the BD signal which is inputted and for switching so as to readout necessary codes every predetermined AddOn line on the basis ofpattern information stored in the ROM. In the switching, a controlsignal SEL is generated from the CPU 302 for always counting the BDsignal so that the addition of dots, which will be explainedhereinlater, is executed.

Explanation will now be made hereinbelow with respect to a control suchthat all of the various additional information is not always added atfixed periods but important information (the manufacturer ID in theembodiment) in the plurality of additional information is added whilechanging the period.

First, when the image processing apparatus starts the printingoperation, the control signal SEL to control so as to read out 12 bits(including the parity bits) showing the manufacturer ID in the register301 is outputted from the CPU 302 to the switching unit.

Subsequently, the control signal SEL to control so as to read out thecodes showing the other additional information (manufacturer ID,apparatus number, model number, and the like) as much as onlypredetermined AddOn lines is outputted from the CPU 302 to the switchingunit.

For the above period of time, the CPU 302 always counts the AddOn lines.Therefore, for example, in case of sequentially adding the otheradditional information in accordance with the order of the manufacturerID→apparatus number→model number, when reaching a predetermined numberof AddOn lines at which the addition of the codes showing themanufacturer ID and the apparatus number is finished, the control signalSEL to control so as to read out the code showing the manufacturer ID isagain outputted from the CPU 302 to the switching unit.

When the reading of the manufacturer ID is subsequently finished, thecontrol signal SEL to control so as to read out the model number insteadof the manufacturer ID and the apparatus number is outputted from theCPU 302 to the switching unit.

When the reading of the model number is finished, the control signal SELto control so as to read out the code indicative of the manufacturer IDis again outputted from the CPU 302 to the switching unit.

By repeating the above processing steps, while the information of arelatively low significance is added one by one, two importantinformation such as a manufacturer ID can be added.

In order to easily execute the foregoing control of AddOn lines, it isdesirable that the AddOn lines corresponding to the codes showing themanufacturer ID, apparatus number, and model number are independent.However, even if such a construction is not used, it is possible tosufficiently execute. In this case, it is sufficient that the controlsignal SEL performs the read control on a unit basis of bits (3 bits inthe embodiment) which can express one AddOn line instead of performingthe read control every kind of additional information as mentionedabove.

The code which was read out while performing the above control isenciphered by the encipherment circuit 305 in a manner similar to theencipherment circuit 305 in FIG. 5. A parity is checked by the paritycheck 306. If an error occurs here, the printing operation is stopped.

The subsequent process to add the AddOn dots is similar to that in FIG.5.

FIG. 2 is a diagram showing a state when AddOn dots (additionalinformation) is added by using the additional dot generation unit 212 inFIG. 1.

A meshed area 702 shown by A×B corresponds to the area 1202 in FIG. 8,namely, to an image area of a unit period which can show all of theinformation.

FIG. 2 differs from the case of FIG. 8 with respect to a point that thenumber of AddOn lines showing the manufacturer ID is doubled (8 lines).Therefore, the number of necessary AddOn lines is equal to 20.

Each dot 701 is the same as the AddOn dot in FIG. 8 and is shown in FIG.7.

In the diagram, an area (for example, AddOn lines 1 to 4) shown by A×Cand an area (for instance, AddOn lines 11 to 14) shown by A×D correspondto the AddOn lines indicative of the manufacturer ID.

In the embodiment, among a plurality of additional information which isadded to the image, since the manufacturer ID is set to the informationwhich needs the maximum decodability, it is controlled so that themanufacturer ID is added twice in a unit area (area 702).

Thus, even if there are causes of periodic elements such as in the casewhere a dot image similar to the dot 701 periodically exists in an imageto which additional information should be added (in the case where theoriginal image is an image such that a dot image always exists in thearea of A×C at the same period as that in the area 702), in the casewhere there is always a trouble or the like of the image process in thearea of A×C at the same period as that of the area 702, or the like,since the same information exists in the area of A×D in the area 702,the additional information (manufacturer ID in this case) can becertainly decoded.

Although the important information has been set to the manufacturer IDin the above embodiment, the invention is not limited to it. The user IDor the factory ID can be also used as important information.

In the above embodiment, each time the other information is added once,the important information is added twice. However, the invention is notlimited to such a method but the important information can be also addeda plurality of number of times such as three or more times in accordancewith the importance.

Each time the other information is added once, the important informationis not added a plurality of number of times but the position of theAddOn line showing the important information can be also varied in thearea of the unit period (702 in FIG. 2, 1202 in FIG. 8).

FIG. 10 is a diagram showing a state where the additional informationwas added by using the above method. An outline of the diagram issimilar to FIG. 8. FIG. 10 differs from FIG. 8 with respect to a pointthat four AddOn lines to show the important information (manufacturer IDin this case) change on the area 1202. In the diagram, in an area 1202 aat the first left upper position of the image, an area E₁ of the firstfour AddOn lines is an area showing the important information. On anarea 1202 b, an area E₂ of the last four AddOn lines changes to the areato indicate the important information. Subsequently, the position of thefour AddOn lines to show the important information is changed like E₃,E₄, . . . .

Thus, even if there is a cause of periodic elements such as in the casewhere a dot image similar to the dot 1201 periodically exists in animage to which the additional information should be added, in the casewhere a trouble or the like in the image process always exists in thearea of E₁ at the same period as that in the area 702, or the like, theadditional information can be certainly decoded.

In the above embodiment, as for the AddOn dots, the additionalinformation is added by the dots 404 and 405 constructed by combiningthe FF area and 00 area as shown in FIG. 7. However, the invention isnot limited to such a method. Dots can be also formed by performing amodulation of +α to the original image with respect to the areacorresponding to the FF area and by executing a modulation of −α to thearea corresponding to the 00 area.

According to this construction, since the density of the original imageis substantially preserved, the deterioration in picture quality can besuppressed as much as possible.

According to the invention as described above, in the case such that theadditional information is added to the input image a plurality of numberof times, a situation such that the additional information to be addedbecomes difficult to be decoded due to causes of some periodic elementssuch that at least a part of the input image is periodical, a trouble orthe like in the image process is periodical, or the like can be avoided.Particularly, in case of burying a plurality of kinds of additionalinformation to the input image, the information having high significancecan be decoded as much as possible.

As a second embodiment of the invention, an image processing apparatususing a color electrophotographing technique is shown. However, theinvention is not limited to it but can be also applied to an imageprocessing apparatus using a technique such as ink jet system, thermaltransfer system, or the like. The invention is not limited to theapparatus invention but a method of performing the processes, which willbe explained hereinlater, software to perform this method, and the likeare also incorporated in the present invention.

In the embodiment, it is now assumed that the image data which isinputted is multi-value image data of M (magenta), C (cyan), Y (yellow),and K (black) each consisting of 8 bits per color and the multi-valueimage data is area sequentially inputted.

It is also assumed that the image processing apparatus (laser beamprinter) of the embodiment has a resolution of 600 dpi and the dotpattern showing the additional information for fake tracking is added toonly the plane of Y. By using this method, it is possible to constructsuch that the additional information is difficult to be discriminated bythe human eyes as much as possible. Even a color image to which theadditional information was added can be used in a manner similar to theoriginal color image before the additional information is added. Theinvention is not limited to the case of adding the additionalinformation for fake tracking. In other words, a case where the name ofauthor who made the original image or the title or the like of the imageis used as additional information is also incorporated in the invention.

FIG. 11 shows a construction of an image processing apparatus which isused in the following embodiment.

Reference numeral 1000 denotes an image processing unit. The imageprocessing unit 1000 sequentially inputs multi-value image data of M, C,Y, and K from external equipment or another equipment in the apparatus,adds addition information, which will be explained hereinlater, to themulti-value image data, and after that, outputs the image data of eachcolor to a laser light emitting unit 1001. The laser light emitting unit1001 emits the laser beam L, which will be explained hereinlater,modulated in accordance with the inputted image data.

The photosensitive drum 100 is uniformly charged to a predeterminedpolarity by the charging device 101. For example, a first latent imageof magenta is formed on the photosensitive drum 100 by the exposure bythe laser beam L. In this case, a desired development bias voltage isapplied to only the developing device Dm of magenta, the latent image ofmagenta is developed, and the first toner image of magenta is formed onthe photosensitive drum 100.

On the other hand, the transfer paper P is fed at a predeterminedtiming. Just before the front edge of the transfer paper reaches thetransfer start position, a transfer bias voltage (+1.8 kV) of a polarity(for example, plus polarity) opposite to that of the toner is applied tothe transfer drum 102. The first toner image on the photosensitive drum100 is transferred onto the transfer paper P. The transfer paper P iselectrostatically adsorbed onto the surface of the transfer drum 102.After that, the residual magenta toner on the photosensitive drum 100 isremoved by the cleaner 103, thereby preparing for the latent imageformation and the developing step of the next color.

Subsequently, in a manner similar to the case of magenta mentionedabove, the second latent image of cyan is formed onto the photosensitivedrum 100 by the laser beam L. The second latent image on thephotosensitive drum 100 is developed by the developing device Dc ofcyan. The second toner image of cyan is formed. The second toner imageof cyan is transferred onto the transfer paper P while matching to theposition of the first toner image of magenta which has already beentransferred to the transfer paper P. In the transfer of the toner imageof the second color, just before the transfer paper reaches the transferunit, a bias voltage of +2.1 kV is applied to the transfer drum 102.

Similarly, the third and fourth latent images of yellow and black aresequentially formed on the photosensitive drum 100 and are sequentiallydeveloped by the developing devices Dy and Db, respectively. The thirdand fourth toner images of yellow and black are sequentially transferredwhile matching to the position of the toner image which has already beentransferred to the transfer paper P. Thus, a full color image in whichthe toner images of four colors were overlapped is formed on thetransfer paper P.

Additional information for fake tracking which is added by the imageprocessing apparatus of the embodiment will now be described.

FIG. 12 shows a state where the additional information was added to theimage shown by the inputted image data in the embodiment. In theembodiment as mentioned above, since the additional information is addedto only the plane of Y, FIG. 12 shows the image shown by the plane of Yof the color image comprising planes of Y, M, C, and K.

Each of dots 1201 existing in FIG. 12 is a dot of a micro areaconstructed by a plurality of pixels. This dot is referred to as anAddOn dot hereinbelow.

In the diagram, a meshed area 1202 is a unit area showing additionalinformation which is added to the color image (plane of yellow) in theembodiment. The unit area 1202 periodically exists in the original colorimage (plane of yellow). By using this method, with respect to the colorimage finally formed after the additional information was added, theadditional information can be analyzed with reference to any one of theareas.

A plurality of lines 1203 called AddOn lines exist in the unit area1202. In the embodiment, it is assumed that 16 lines exist in the mainscan direction. It is also assumed that as for the foregoing AddOn dots,one AddOn dot is arranged on each AddOn line in the unit area 1202. Aswill be explained hereinlater, the additional information can showvarious information by the position (phase) of the AddOn dot on eachAddOn line. As various information, the product name, manufacturingnumber, manufacturer name, and the like of the image processingapparatus can be allocated.

A reference dot 1204 to prevent that the arranging direction of theAddOn dot to show the additional information is erroneouslydiscriminated is added in the unit area 1202. The position of thereference dot is always fixed. In the embodiment, the reference dot 1204is added onto the 0th and 7th AddOn lines together with the AddOn dot.By using this method, the AddOn line indicative of the start of the unitarea can be specified and the arranging direction of the AddOn lines 0to 15 can be specified.

FIG. 14 is a block diagram of an AddOn dot adding processing unitincluded in the image processing unit 1000 in FIG. 11. The additionalinformation (product name of the apparatus, manufacturing number,manufacturer name, and the like) stored in an EEPROM 1401 isautomatically loaded into a register 1402 in the CPU when the powersource of the image processing apparatus is turned on.

FIG. 13 shows an internal construction of the register 1402. In theregister 1402, codes are stored in addresses F000 to F00A. Total 12 bitscomprising 8 bits of the address F000 shown by a hatched region andupper 4 bits of the address F0001 shown by a hatched region in thediagram correspond to an area only for use of the manufacturer name(manufacturer ID) mentioned above. The peculiar ID number assigned everymanufacturer who manufactured the image processing apparatus is storedin this area. The codes indicative of the product name of the imageprocessing apparatus, manufacturing number, and the like which haveuniquely been determined by each manufacturer are stored in the otherareas (lower 4 bits of the address F0001, and F002 to F00A).

Besides the foregoing additional information, the fixed bit in which afixed value is stored and the parity bits for parity check are alsostored in the register 1402.

When the image processing apparatus receives a command to print thecolor image, the foregoing additional information (product name of theapparatus, manufacturing number, manufacturer name, and the like) isinputted to an encipherment circuit 1405 and is enciphered.

The enciphered additional information is inputted to a parity checkcircuit 1406 and the parity and the fixed bit are checked. When an erroroccurs here, it is regarded that the additional information has beenremodeled, thereby performing a control to stop the printing operation.

A main scan counter 1407 executes the counting operation in response tothe clock signal PCLK in the main scan direction of the image data andgenerates an ON signal at a position where the AddOn dot should be addedin accordance with a code which is loaded by the parity check 1406. Asubscan counter 1408 executes the counting operation in accordance withthe clock signal BD in the subscan direction and generates an ON signalin the AddOn line.

An AddOn dot generation circuit 1409 receives the AddOn dot-shapedparameter which is stored into an ROM 1403 in the CPU, forms the AddOndot only when all of an AddOn permission signal which is turned on onlywhen the yellow plane of the image data is transmitted, the main scancounter 1407, and the subscan counter 1408 are ON, turns on the AddOnsignal, and sends.

When the AddOn signal is OFF, an AddOn adding circuit 1404 transmits asit is to the image data which is inputted. When the AddOn signal is ON,the AddOn adding circuit 1404 converts it into the AddOn dot and sendsit. Thus, the additional information (AddOn dot) is formed as shown inFIG. 12.

A method of analyzing the additional information added to the image datain the embodiment, namely, a method of showing the additionalinformation by the AddOn dot will now be described.

FIG. 15 enlargedly shows the n-th and (n+1)th AddOn lines in the unitarea 1202 in FIG. 12. Explanation will now be made with respect to the(n+1)th AddOn line. A phase difference using the AddOn dot on the n-thAddOn line as a reference is assigned to 0 to 7 (3 bits) as shown in thediagram, thereby allowing the AddOn dot to be added to the positioncorresponding to the 3-bit information to be added in the (n+1)th AddOnline. Therefore, information of 3 bits can be expressed by one AddOnline (AddOn dot). Thus, since there are 16 AddOn lines in theembodiment, additional information of total 48 bits can be added.

However, the invention is not limited to this method but the additionalinformation can be also added by another method. For example, by addinga plurality of AddOn dots onto each AddOn line, more additionalinformation can be also added.

As for the analysis of the phase difference, for example, the colorimage to which the additional information was added is read by ascanner, only the image of the plane of Y (yellow) is extracted andtransmitted to a host computer, and an interval between the AddOn dotsis measured on a monitor of the host computer, so that the phasedifference can be measured. On the basis of the measured phasedifference, the code of each AddOn line is searched and the searchedcodes are arranged as shown in FIG. 16 and are binarized. After that,the binary codes are assigned as address information of a00 to a30 andb00 to b112.

a00 to a32 indicate the manufacturer ID (manufacturer name) and a22,a30, a31, and a32 are parity bits.

First, when the manufacturer ID is analyzed, a00 to a32 are arranged asshown in FIG. 17 and it is confirmed that a22, a30, a31, and a32 becomeeven parities in the arrow direction in the diagram. If an error isdetected by the parity check, it is regarded that there is a readingmistake (analysis mistake) of the manufacturer ID and the operation isre-executed from the measurement.

If no error is detected by the parity check, a00 to a21 are arranged asfollows, thereby obtaining the manufacturer ID.

Manufacturer ID=(a21, a20, a12, a11, a10, a02, a01, a00)

In the example of FIG. 16, the manufacturer ID is as follows.

Manufacturer ID = (a21, a20, a12, a11,    a10, a02, a01, a00) = 0, 0, 1,0, 0, 0, 1, 0(B) = 34(D)

The manufacturer who manufactured the image processing apparatus whichwas used for the formation of the color image is analyzed by theobtained manufacturer ID.

After the manufacturer ID was analyzed, the additional information suchas product name, manufacturing number, and the like can be analyzed bythe method according to each manufacturer. This is because there is apossibility such that the adding method of the additional informationsuch as product name, manufacturing number, and the like differs everymanufacturer. Therefore, the parity bits are independently added to themanufacturer ID and the product name and manufacturing number,respectively.

Subsequently, with respect to b00 to b112 (including the parity bits)showing the additional information such as product name, manufacturingnumber, and the like, they are analyzed (parity check) independently ofthe manufacturer ID.

As for the additional information of b00 to b112, after the decoding ofthe additional information of b00 to b112 and the parity check wereperformed by using the method suitable for each manufacturer, the modelnumber, apparatus number, and the like are obtained.

As mentioned above, by independently adding the parity bits to themanufacturer ID (manufacturer name) and the product name andmanufacturing number (model number, apparatus number, and the like canbe also used), even in case of adding the additional information of themanufacturer ID and the additional information such as product name,manufacturing number, and the like to the image by different methods,whether the various analyzed additional information is accurate or notcan be certainly discriminated.

FIG. 19 shows a conceptual diagram of the additional information such asmanufacturer ID, product name, and manufacturing number added in theabove embodiment.

In FIG. 19, reference numeral 1202 corresponds to the unit area 1202 inFIG. 12. The manufacturer ID is added (expressed) by using the AddOnlines (AddOn lines 0 to 3) of an upper area 1901 of the unit area 1202.The product name and the manufacturing number are added (expressed) byusing the AddOn lines (AddOn lines 4 to 15) in a lower area 1902 of theunit area 1202.

A procedure to decode the additional information will now be explainedwith reference to FIG. 18.

When the decoding is started, the color image is first read by ascanner. Since the additional information of the embodiment has beenadded to the yellow plane, only the yellow plane is read (step S1).Subsequently, the reference dot is detected, the head of the AddOn lineand the direction of the AddOn line are recognized, and phasedifferences among the AddOn lines 0 to 3 (AddOn lines 15 and 0; 0 and 1;1 and 2; and 2 and 3) are measured (step S2).

The codes of the AddOn lines 0 to 3 are obtained on the basis of themeasured phase differences (step S3) and are binarized and are assignedto a00 to a32 (step S4). The parity check of FIG. 17 mentioned above issubsequently executed (step S5). If there is an error, the operation isre-executed from the measurement of the phase differences (step S2). Ifthere is no error, the manufacturer ID is obtained (step S6).

Phase differences among the AddOn lines 4 to 15 are subsequentlymeasured (step S7). On the basis of the measured phase differences, thecodes of the AddOn lines 4 to 15 are obtained (step S8) and arebinarized and are assigned to b00 to b112 (step S9).

A check is made to see if the manufacturer ID obtained in step S6indicates company A (step S10). If it is the company A, a module forcompany A is activated (step S11). The module for company A rearrangesb00 to b112 in accordance with the rules of company A and the paritycheck and the like are executed. After that, the product name,manufacturing number, and the like are obtained.

When the manufacturer ID does not indicate company Ain step S10, a checkis made to see if it indicates company B (step S12). If it indicatescompany B, a module for company B is activated (step S13). In a mannersimilar to step S11, the module for company B rearranges b00 to b112 inaccordance with the rules of company B and the parity check and the likeare executed. After that, the product name, manufacturing number, andthe like are obtained.

Similarly, when the manufacturer ID does not indicate company B in stepS12, the manufacturer IDs are sequentially checked only a number oftimes as many as the number of registered manufacturers such thatcompany C, company D, . . . .

In the embodiment, although the number of AddOn lines to store theinformation of each manufacturer has been fixed to 12 AddOn lines 4 to15, the number of AddOn lines can be also varied every manufacturer.

In the embodiment, as for the parity bits, parity bits such that anerror detection can be merely performed are added to the manufacturer IDcorresponding to the area 1901 in FIG. 19 and the product name andmanufacturing number corresponding to the area 1902 in FIG. 19,respectively. However, the invention is not limited to this method. Anerror correction code such that an error of the additional informationcan be corrected can be also provided for each of the additionalinformation corresponding to the areas 1901 and 1902.

Thus, even if there is an error in the analysis of the additionalinformation, the operation to again read the phase differences can beomitted.

Further, in the case where it is considered that significance of theadditional information (manufacturer ID) in the area 1901 is higher thanthat of the additional information (product name, manufacturing number,and the like) corresponding to the area 1902 such as a case where thereis a possibility such that unless the additional information of the area1901 can be analyzed, the area 1902 cannot be analyzed or the like, itis also possible to give an error correction code of a high errorcorrecting ability to the additional information of the area 1901 and togive an error correction code of a lower error correcting ability thanthat in the area 1901 to the area 1902.

By using this method, the important portion of the additionalinformation can be certainly analyzed. Specifically speaking, since themanufacturer ID can be certainly analyzed, a method for subsequentlyanalyzing the product name, manufacturing number, and the like can bedetermined.

Although the embodiment has been described above on the assumption thatthe method of adding the manufacturer ID into the area 1901 and themethod of adding the product name, manufacturing number, and the likeinto the area 1902 are the same method, the invention is not limited tothis construction but also includes a case where the adding methods ofthe additional information to the areas 1901 and 1902 are different.

That is, in the embodiment, since the manufacturer ID which can specifythe adding method of the area 1902 is added to the area 1901 differentfrom the area 1902, there is an effect such that even if the addingmethods of the additional information of the areas 1901 and 1902 aredifferent, by sequentially analyzing in accordance with the order of theareas 1901 and 1902 as mentioned above, all of the additionalinformation can be sufficiently decoded.

In the above embodiment, although the additional information has beenadded by the AddOn dot in which the original image is merely modulatedto the highest density, the invention is not limited to such aconstruction. For example, even if one AddOn dot is constructed bycombining an area to add +α to the density of the original image and anarea to subtract a from the density of the original image, theadditional information can be sufficiently analyzed. In this case, sincethe density of the original image is preserved, the picture quality thatis further higher than that in the foregoing embodiment can bepreferably held. One AddOn dot can be also constructed by combining anarea to modulate the density of the original image to the highestdensity and an area to modulate it to the lowest density. By using thismethod, the AddOn dot can be easily decoded irrespective of the densityof the original image.

According to the invention as described above, in the case wherepredetermined additional information is added to the input image by oneof a plurality of methods which are generally considered so that it isdifficult to discriminate by the human eyes, another information whichcan specify the method of adding the predetermined additionalinformation is added so that it is difficult to discriminate by thehuman eyes. Therefore, the additional information can be efficientlydecoded from the image to which the predetermined additional informationwas added.

The first additional information including the error correction codehaving the first error correcting ability is added to the input image sothat it is difficult to discriminate by the human eyes and the secondadditional information including the error correction code having thesecond error correcting ability different from the first errorcorrecting ability is added so that it is difficult to discriminate bythe human eyes. Therefore, when the importance of a plurality ofadditional information which is added to the image so that it isdifficult to discriminate by the human eyes is different, the additionalinformation having the high importance can be certainly decoded.

The invention is not limited to each of the above embodiments but can beapplied as a part of a system constructed by a plurality of equipment(for example, host computer, interface equipment, reader, printer, andthe like) or can be also applied to a part of an apparatus comprisingone equipment (for instance, copying apparatus or facsimile apparatus).

The invention is not limited to only the apparatus and method forrealizing the above embodiments. The invention also incorporates a casewhere program codes of software to realize the embodiment are suppliedto a computer (CPU, MPU) in the system or apparatus and the computer ofthe system or apparatus makes the various devices operative inaccordance with the program codes, thereby realizing the embodiment.

In this case, the program codes themselves of the software realize thefunction of the embodiment. The program codes themselves and means forsupplying the program codes to the computer, specifically speaking, astorage medium in which the program codes have been stored are alsoincorporated in the scope of the invention.

As a storage medium to store the program codes as mentioned above, forexample, it is possible to use a floppy disk, a hard disk, an opticaldisk, a magnetooptic disk, a CD-ROM, a magnetic tape, a non-volatilememory card, an ROM, or the like.

Not only in the case where the computer controls various devices inaccordance with only the supplied program codes, thereby realizing thefunction of the embodiment but also in the case where the program codescooperate together with the OS (Operating System) which operates on thecomputer or another application software or the like, the above programcodes are also incorporated in the scope of the invention.

Further, the invention also incorporates a case where the suppliedprogram codes are stored into a memory provided for a function expansionboard of the computer or a function expanding unit connected to thecomputer and, after that, a CPU or the like provided for the functionexpansion board or function expanding unit executes a part or all of theactual processes on the basis of an instruction of the program codes andthe embodiment is realized by the processes.

The present invention is not limited to the foregoing embodiments butmany modifications and variations are possible within the spirit andscope of the appended claims of the invention.

What is claimed is:
 1. An image processing apparatus comprising: addingmeans for adding first additional information including a first errorcorrection code to an input image so that it is difficult todiscriminate by the human eyes and for adding second additionalinformation including a second error correction code so that it isdifficult to discriminate by the human eyes; and output means foroutputting the image to which predetermined additional information wasadded by said adding means to an image forming unit, wherein the firsterror correction code and the second error correction code are used toanalyze the first additional information and the second additionalinformation respectively, and wherein a precision of the analyzingdiffers when using the first error correction code from when using thesecond error correction code.
 2. An apparatus according to claim 1,wherein said first additional information is information which canspecify an adding method of said second additional information by saidadding means.
 3. An apparatus according to claim 1, wherein said firsterror correcting ability is higher than said second error correctingability.
 4. An apparatus according to claim 1, wherein a method ofadding said first additional information and a method of adding saidsecond additional information are different.
 5. An apparatus accordingto claim 1, wherein a method of adding said first additional informationand a method of adding said second additional information are the same.6. An apparatus according to claim 1, wherein said input image is acolor image constructed by planes of a plurality of colors, and saidadding means adds said first and second additional information to only apartial plane among said planes of said plurality of colors.
 7. Anapparatus according to claim 1, wherein said first additionalinformation is a manufacturer ID of said image processing apparatus. 8.An apparatus according to claim 1, wherein said second additionalinformation is a model number or a product name of said image processingapparatus.
 9. An apparatus according to claim 1, wherein said secondadditional information is an apparatus number or a manufacturing numberof said image processing apparatus.
 10. An apparatus according to claim1, further comprising said image forming unit.
 11. An apparatusaccording to claim 1, wherein said first additional information is apattern constructed by a plurality of dots.
 12. An apparatus accordingto claim 1, wherein said second additional information is a patternconstructed by a plurality of dots.
 13. An apparatus according to claim1, wherein said additional information is periodically added to saidinput image.
 14. An apparatus according to claim 1, wherein said firstadditional information is added to a first area of said input image andsaid second additional information is added to a second area differentfrom said first area.
 15. An image processing method comprising: anadding step of adding first additional information including a firsterror correction code to an input image so that it is difficult todiscriminate by the human eyes and adding second additional informationincluding a second error correction code so that it is difficult todiscriminate by the human eyes; and an outputting step of outputting theimage to which predetermined additional information was added by saidadding step to an image forming unit, wherein the first error correctioncode and the second error correction code are used to analyze the firstadditional information and the second additional informationrespectively, and wherein a precision of the analyzing differs whenusing the first error correction code from when using the second errorcorrection code.
 16. A storage medium for storing a computer-readableimage processing program comprising code for performing: an adding stepof adding first additional information including a first errorcorrection code to an input image so that it is difficult todiscriminate by the human eyes and adding second additional informationincluding a second error correction code so that it is difficult todiscriminate by the human eyes; and an outputting step of outputting theimage to which predetermined additional information was added by saidadding step to an image forming unit, wherein the first error correctioncode and the second error correction code are used to analyze the firstadditional information and the second additional informationrespectively, and wherein a precision of the analyzing differs whenusing the first error correction code from when using the second errorcorrection code.